The bit rate of OTN (Optical Transport network) is defined on the basis of the bit rate of SONET (Synchronous Optical Network)/SDH (Synchronous Digital Hierarchy). Therefore, it is necessary to expand the OTN standard whenever Ethernet (registered trademark) or a fiber channel with a different bit rate is newly added.
However, it is not preferable to expand the standard whenever a new client signal appears. Therefore, ITU-T Rec. G. 709 (December/2009) uses GMP (Generic Mapping Procedure) in order to respond to client signals with any bit rate which will appear in the future. GMP is a method for mapping the client signal with a bit rate less than the capacity of a payload to the payload area. As shown in FIG. 7, a transmitting unit distributes data and stuff in the payload area. As shown in FIG. 8, JC bytes JC1 to JC6 for adjusting the bit rate are stored in an OH (Over Head). In addition, a term “stuff” described in the following specification and drawings is a term defined in ITU-T Rec. G. 709 (December/2009) standard.
The JC bytes JC1 and JC2 indicate a parameter Cm indicating an integer part of the amount of data included in the payload area which is calculated by the calculating unit and the varying conditions of the parameter Cm indicating the integer part, respectively. The JC byte JC3 is CRC (Cyclic Redundancy Check) of the JC byte JC1 and the JC byte JC2. The JC bytes JC4 and JC5 are the sum ΣCnD of the remainders CnD for each frame when the amount of data included in the payload area is divided by Cm and are represented in hexadecimal notation. The JC byte JC6 is CRC of the JC byte JC4 and the JC byte JC5. A receiving unit detects the OPU frame from a received signal, extracts the JC bytes arranged in the OH, calculates each parameter inserted by the transmitter side using the JC bytes JC1 to JC6, moves the amount of extracted data according to the procedure corresponding to the parameters and the varying conditions, and receives the amount of data equal to the amount of data inserted by transmitting unit.